FACTOR AFFECTING SOIL SUCTION

The suction in soils depends mainly on the following factors:

1. Particle Size

In general the smaller the particle size, the greater is the soil suction.The soils with fine particles have a large number of small pores with small radii of menisci. It results in large capillary rise and hence greater suction.

2. Water Content

 Water content is also known natural moisture content, is the ratio of the weight of water to the weight of the solids in a given mass of soil.As the water content of a soil decreases, the soil suction increases and it attains the maximum value when the soil is dry.

3. Soil Structure 

Soil structure describes the arrangement of the solid parts of the soil and of the pore space located between them.The soil structure governs the size of interstices in the soils.As the soil suction depends upon the size of interstices, a charge in the soil structure affects the soil suction.

4. Denseness of Soil

As the denseness of a soil increases, generally soil suction increases.When the soil is loose, with a low density the pores are of large radius and the soil suction is low.

5. Temperature

A rise in temperature causes a reduction in surface tension (Ts) of the water.Consequently, the soil suction decreases as the temperature increases.

6. Dissolved Salts

The surface tension of water increases with an increase in impurities, such as salt.

7. Angle of Contact

The angle of contact between water and soil particles depends upon the mineralogical composition of soils.As the angle of contact (𝛉) increases, the soil suction decreases.The soil suction is maximum when the angle of contact is zero.

8. Wetting Cycle

As discussed in the preceding section, for the same water content, the soil suction is greater during the drying cycle than in the wetting cycle.